1. Field of the Invention
The present invention describes a method for continuously producing a silicone polymer-filler mixture in a continuous kneader extruder.
2. Background Information
Silicone polymer-filler mixtures are used as a base for various silicone rubber compositions, silicone compounds and greases, etc. These mixtures are generally produced by first polymerizing silicone oligomer into a silicone polymer with the desired viscosity and then mechanically mixing the resulting silicone polymer with the selected filler. However, such methods require 2 different types of processes, necessitating a separate polymerization apparatus and mixing apparatus. As a result, the process is complicated and disadvantageous on a cost basis. In addition, it is difficult in such methods to mix and disperse filler into high-viscosity silicone polymers and large amounts of energy are consumed. This particular problem becomes significant when the molecular weight of the silicone polymer is as high as that of a so-called gum.
On the other hand, British Pat. No. 1,325,654 published Aug. 8, 1973, discloses a method in which a silicone polymer-filler mixture is produced by polymerization of organosiloxane oligomer in the presence of filler. However, this method is a batch process and suffers from the following problems: production of silicone polymer with the desired degree of polymerization requires a long time, the process is complicated and heterogeneous gel material is produced in the silicone polymer-filler mixture product.
U.S. Pat. No. 4,433,096, issued Feb. 21, 1984 to Bokerman, et al. teaches a method of polymerizing polydiorganosiloxane in the presence of filler, using basic diorganosilanolates as catalysts. The use of trifluoromethane sulfonic acid is taught in U.S. Pat. No. 4,448,927, issued May 15, 1984, to Falender, et al. The use of a catalytic amount of sulfuric or sulfonic acid is described in U.S. Pat. No. 4,482,670, issued Nov. 13, 1984 to Saam, et al. A mixture of quaternary ammonium carboxylate and carboxylic acid is disclosed in U.S. Pat. No. 4,486,567, issued Dec. 4, 1984 to Bowman, et al. None of these methods disclose a continuous method of producing a silicone polymer-filler mixture, but describe batch methods of production.